The invention generally pertains to molybdenum carbides, and more specifically, to apparatus and methods for production of molybdenum carbide.
Hydrogen reacts with oxygen to generate energy while producing water instead of the pollutants typically associated with the combustion of fossil fuels. Therefore, hydrogen is potentially a significant source of xe2x80x9ccleanxe2x80x9d energy. Among other uses, hydrogen is also used on an industrial basis for chemical synthesis (e.g., methanol and ammonia synthesis).
Sources of hydrogen include methane, a significant component of relatively abundant natural gas. Processes such as steam reforming and dry reforming of methane may be used to produce hydrogen gas and carbon monoxide. However, the catalysts required for these reactions are typically made of expensive noble metals, such as elemental gold, platinum, iridium, ruthenium, and nickel. In addition, these catalysts must be replaced frequently as they tend to become plugged and eventually deactivated by carbon deposits. Molybdenum carbides (MoC and/or Mo2C) have been shown to be a viable and less expensive alternative to noble metal catalysts for a variety of reactions, including oxidation of methane to form hydrogen gas.
Various processes have been developed for producing molybdenum carbide. According to one such process for producing Mo2C, ammonium molybdate powder is loaded into a quartz liner and placed into a rotary kiln. The system is first purged with nitrogen, then a hydrogen and carbon monoxide mixture is introduced. Initially, the temperature is set to 300xc2x0 C. to decompose the ammonium molybdate. Thereafter, the temperature may only be ramped between 2xc2x0 C. and 20xc2x0 C. per minute. The Mo2C forms during a three to five hour soak at a temperature between 550xc2x0 C. and 600xc2x0 C. The reactor is then cooled, and the Mo2C powder may be passivated with diluted oxygen or air after the powder cools to room temperature.
However, this process for producing molybdenum carbide requires the temperature ramp rate not exceed 20xc2x0 C. per minute, and is thus a time-consuming process. In addition, this is a batch process, which slows production and increases production costs.
An embodiment of a method for producing molybdenum carbide may comprise the steps of: heating a precursor material in a first heating zone in the presence of a reducing gas and a carbonizing gas, the first heating zone having a first temperature; and moving the precursor material into a second heating zone to form the molybdenum carbide from the precursor material, the second heating zone having a second temperature, the second temperature being at least 100xc2x0 C. hotter than the first temperature.